Windows discussions and local services.
Room-side condensation on desert-facing replacement windows: humidity or installation issue?
Discussion options
I’m trying to narrow down recurring moisture on the **room side** of replacement windows that face west. It shows up mainly in a bedroom, not the other rooms, and is worst in the morning after the door has stayed closed overnight.
What should I check first?
- Indoor temperature and relative humidity at the time it appears
- Whether the bedroom has adequate supply-air and return-air movement
- Whether the moisture is on the glass, between the panes, or along the frame and sill
- Whether the glass feels unusually cold compared with the surrounding wall
- Possible installation issues such as gaps, poor shimming, missing insulation, or an incomplete interior air seal
The windows are double-pane, but I don’t know the glass temperature, U-factor, or SHGC. If the moisture is only on the room-side surface, does that usually point to indoor humidity meeting a cold glass surface? At what humidity level would you stop adjusting ventilation and humidity and have the installer inspect the window instead?
1 reply
The “worst in the morning after the door has stayed closed” detail makes a bedroom humidity check especially useful, but record the numbers when the condensation is actually visible, not hours later. Note room temperature, relative humidity, and whether the moisture is centered on the glass or concentrated at the frame and sill.
Then compare the result with the window manufacturer’s published condensation-resistance rating, if available, or with local dew-point guidance. A cold west-facing pane can still collect moisture at ordinary winter humidity, depending on the glass package and outdoor temperature. But persistent condensation at fairly modest indoor humidity, particularly along the frame or sill rather than across the glass, would make me ask the installer to check for air leakage, poor shimming, or missing perimeter insulation. A small temperature and humidity logger left in that bedroom can make the pattern much easier to document.
Join the conversation
Share your experience or ask a follow-up question.